Private drains, public pains

Public dissatisfaction over the number of times sewage is discharged into Gisborne waterways grow louder with every heavy rain we get, and Andrew Ashton sits down with two of the men gearing up for the job of going house-to-house to solve the problem. It's the engineering equivalent of urban warfare.

Public dissatisfaction over the number of times sewage is discharged into Gisborne waterways grow louder with every heavy rain we get, and Andrew Ashton sits down with two of the men gearing up for the job of going house-to-house to solve the problem. It's the engineering equivalent of urban warfare.

CLEAN-UP CREW: Gisborne District Council’s Neville West (left) and David Wilson at the Wainui Road wet weather pump station. Picture by Paul Rickard
BEFORE AND AFTER: Swathes of red indicate the areas of the Gisborne wastewater network identified as being at-risk of overflow and flooding (above). The council says this can be reduced dramatically (next picture) if a way can be found to implement $13.2 million of drainage improvements on private properties.
This image shows the expected capacity of the network after recommended pipe upgrades.
DOWNSTREAM EFFECTS: Fewer warnings to avoid swimming is one of the aims of GDC’s DrainWise project, which aims to cut the number of times wastewater is discharged to city rivers from four a year to one every two years.

HAVING gone through several committee stages over the last year, Gisborne District Council’s DrainWise Wastewater Discharge Reduction Plan has considered at length how the city’s failing wastewater and stormwater systems can be brought up to scratch.

The cost, however, is high and the work programme is complicated — because it will have to resolve drainage issues on more than 1000 private properties.

The DrainWise plan pulls together and builds on a host of past and ongoing drain-related projects, dating back to 1988 and the then Gisborne City Council.

GDC water utilities manager Neville West says at that time the pipe capacity was exceeded when it rained by a factor of 16. Two recommendations were then made to upgrade sewer pipes at the same time as improving the stormwater network.

Mr West first started dealing with the issue in the early 1990s and since then he estimates “in excess” of $25 million has been spent on upgrades and addressing stormwater problems, mainly on the council’s portion of the system.

“What we’ve found now is, while those stormwater fixes were done, what didn’t happen was anything to deal with flooding on private property and those owners not connecting to the council system.

“We have had some improvements — in most cases when we have to open the scours, we are down to only discharging into the main river and Russell Street pump station — prior to that we opened them all.

Mr West says the overall wastewater system is 50 percent owned by the council, while the other half is privately owned.

“The council’s focus has to date been on what it can achieve to benefit the network without imposing costs on individual ratepayers. We are still working on the council-owned network and are maintaining and upgrading our network, but we have got to the point now where we are still having overflows — so we are now looking at entering private properties as the main rationale for improvement.”

Issues of floodwater flowing over and into gully traps, issues with leaking gully traps, and roof water being piped into gully traps, had been identified as the three “high impact” network issues.

“It only takes two properties flooding or four downpipes going into gully traps to cause complete inundation of the nearby wastewater pipes — which is equivalent to 100 houses discharging their normal wastewater.”

Computer modelling has now re-examined the early work and, with the help of digital aerial photography (Lidar), which performs the job of a “horde of surveyors”, got ground levels down to an accuracy of 50mm. These models show where stormwater ponding can be expected, and identify at-risk properties.

The modelling and digital aerial photography have identified more than 1000 at-risk properties across a 100ha area of Kaiti alone.

Council seeking permanent solutions

While previous on-property issues had only been dealt with by way of temporary fixes, so as not to impact on property owner costs, the council is now looking at more permanent solutions.

“To get a permanent fix we need to get rid of the stormwater first and then raise the gully traps,” says Mr West.

GDC director of Lifelines David Wilson says some people have devised ingenious home-made solutions to pump water out of their properties, but that has a knock on effect for neighbours.

“Yes their garage is not getting wet, but we want to know if your property has water issues so we can get that stormwater off your property and get it where it’s supposed to be. We can fix the problem — rather than pumping it into our wastewater network where we don’t want it.

“It’s that type of behaviour we are trying to completely stop,” says Mr Wilson.

“The modelling can show us where there might be an issue but we need people to come clean and tell us.

“If you have a huge pond in your backyard every time it rains, we want to know so we can send someone out. A lot of the time we find that water is draining into the neighbour’s gully trap.”

A recent case in Turenne Street involved finding out flooding across five properties had all been going into just one gully trap.

Mr Wilson says changes in ownership of properties, and stories of renters feeling bullied into keeping quiet by landlords, were also a problem.

“We end up chasing our tails and people get away with bit-fixes because properties change hands and tenants change.

“We need to fix it right and make it permanent.”

The council could help get rid of the stormwater permanently for people, if they were willing to come forward.

It was now time for a conversation with the community to find a way forward that didn’t just involve “diggers and drains”.

“We can’t stress enough it’s only working with the community that will get this problem sorted.”

Consultation with community

The council has a range of tools to work with the community on this issue that it will be consulting on through the Long-Term Plan process.

“It becomes an issue of how much does the ratepayer pay for those properties? If the community decides it’s a ratepayer-funded thing to reduce wastewater being discharged into our rivers and on to private property, then that’s fine — but we need to have that conversation . . . $13.2 million is the estimate of how much it will take to fix all the stormwater flooding issues we know about on private property.”

That was a “huge” amount and would solve the largest portion of the overall problem, but the community had to decide if it would be ratepayer-funded or a case of every house for itself.

“The issue we can’t get around is it’s no use us building bigger pipes out on the street, we actually have to fix the problem at source rather than being the ambulance at the bottom of the cliff — which is what we have been doing.

“We’ve made some big improvements but we still have not finished off the bit that’s feeding the problem.”

That was “just” the problem of direct inflow — the matter of infiltration from cracked pipes was another problem.

The amount of work it would take to fix all issues on private properties meant costs could only be estimated.

“The problem is it can cost anything from a couple of hundred dollars to fix a cracked gully trap to $8000 to $10,000 for complete upgrade of pipes out to the street.”

The increase in utility services on the roadside, such as ultra-fast broadband, has complicated matters and increased the cost of work if pipes are being laid out to the kerb and channel or open drains.

Including the estimated $13.2m to tackle private property issues, estimates to provide a long-term solution to greatly reduce overflows and create a sustainable wastewater network — with the aim to achieve a level of service that would have just one discharge per two years — are estimated at $38m to $80m or more, and will vary depending on who pays for what.

Mr Wilson pointed out that councils across New Zealand were grappling with similar “expensive” issues. In Auckland the cost is in excess of $1 billion.

The solution to the problem here was not as expensive, but just as complicated.

“It’s not an easy fix. It’s property to property, pipe by pipe.”

HAVING gone through several committee stages over the last year, Gisborne District Council’s DrainWise Wastewater Discharge Reduction Plan has considered at length how the city’s failing wastewater and stormwater systems can be brought up to scratch.

The cost, however, is high and the work programme is complicated — because it will have to resolve drainage issues on more than 1000 private properties.

The DrainWise plan pulls together and builds on a host of past and ongoing drain-related projects, dating back to 1988 and the then Gisborne City Council.

GDC water utilities manager Neville West says at that time the pipe capacity was exceeded when it rained by a factor of 16. Two recommendations were then made to upgrade sewer pipes at the same time as improving the stormwater network.

Mr West first started dealing with the issue in the early 1990s and since then he estimates “in excess” of $25 million has been spent on upgrades and addressing stormwater problems, mainly on the council’s portion of the system.

“What we’ve found now is, while those stormwater fixes were done, what didn’t happen was anything to deal with flooding on private property and those owners not connecting to the council system.

“We have had some improvements — in most cases when we have to open the scours, we are down to only discharging into the main river and Russell Street pump station — prior to that we opened them all.

Mr West says the overall wastewater system is 50 percent owned by the council, while the other half is privately owned.

“The council’s focus has to date been on what it can achieve to benefit the network without imposing costs on individual ratepayers. We are still working on the council-owned network and are maintaining and upgrading our network, but we have got to the point now where we are still having overflows — so we are now looking at entering private properties as the main rationale for improvement.”

Issues of floodwater flowing over and into gully traps, issues with leaking gully traps, and roof water being piped into gully traps, had been identified as the three “high impact” network issues.

“It only takes two properties flooding or four downpipes going into gully traps to cause complete inundation of the nearby wastewater pipes — which is equivalent to 100 houses discharging their normal wastewater.”

Computer modelling has now re-examined the early work and, with the help of digital aerial photography (Lidar), which performs the job of a “horde of surveyors”, got ground levels down to an accuracy of 50mm. These models show where stormwater ponding can be expected, and identify at-risk properties.

The modelling and digital aerial photography have identified more than 1000 at-risk properties across a 100ha area of Kaiti alone.

Council seeking permanent solutions

While previous on-property issues had only been dealt with by way of temporary fixes, so as not to impact on property owner costs, the council is now looking at more permanent solutions.

“To get a permanent fix we need to get rid of the stormwater first and then raise the gully traps,” says Mr West.

GDC director of Lifelines David Wilson says some people have devised ingenious home-made solutions to pump water out of their properties, but that has a knock on effect for neighbours.

“Yes their garage is not getting wet, but we want to know if your property has water issues so we can get that stormwater off your property and get it where it’s supposed to be. We can fix the problem — rather than pumping it into our wastewater network where we don’t want it.

“It’s that type of behaviour we are trying to completely stop,” says Mr Wilson.

“The modelling can show us where there might be an issue but we need people to come clean and tell us.

“If you have a huge pond in your backyard every time it rains, we want to know so we can send someone out. A lot of the time we find that water is draining into the neighbour’s gully trap.”

A recent case in Turenne Street involved finding out flooding across five properties had all been going into just one gully trap.

Mr Wilson says changes in ownership of properties, and stories of renters feeling bullied into keeping quiet by landlords, were also a problem.

“We end up chasing our tails and people get away with bit-fixes because properties change hands and tenants change.

“We need to fix it right and make it permanent.”

The council could help get rid of the stormwater permanently for people, if they were willing to come forward.

It was now time for a conversation with the community to find a way forward that didn’t just involve “diggers and drains”.

“We can’t stress enough it’s only working with the community that will get this problem sorted.”

Consultation with community

The council has a range of tools to work with the community on this issue that it will be consulting on through the Long-Term Plan process.

“It becomes an issue of how much does the ratepayer pay for those properties? If the community decides it’s a ratepayer-funded thing to reduce wastewater being discharged into our rivers and on to private property, then that’s fine — but we need to have that conversation . . . $13.2 million is the estimate of how much it will take to fix all the stormwater flooding issues we know about on private property.”

That was a “huge” amount and would solve the largest portion of the overall problem, but the community had to decide if it would be ratepayer-funded or a case of every house for itself.

“The issue we can’t get around is it’s no use us building bigger pipes out on the street, we actually have to fix the problem at source rather than being the ambulance at the bottom of the cliff — which is what we have been doing.

“We’ve made some big improvements but we still have not finished off the bit that’s feeding the problem.”

That was “just” the problem of direct inflow — the matter of infiltration from cracked pipes was another problem.

The amount of work it would take to fix all issues on private properties meant costs could only be estimated.

“The problem is it can cost anything from a couple of hundred dollars to fix a cracked gully trap to $8000 to $10,000 for complete upgrade of pipes out to the street.”

The increase in utility services on the roadside, such as ultra-fast broadband, has complicated matters and increased the cost of work if pipes are being laid out to the kerb and channel or open drains.

Including the estimated $13.2m to tackle private property issues, estimates to provide a long-term solution to greatly reduce overflows and create a sustainable wastewater network — with the aim to achieve a level of service that would have just one discharge per two years — are estimated at $38m to $80m or more, and will vary depending on who pays for what.

Mr Wilson pointed out that councils across New Zealand were grappling with similar “expensive” issues. In Auckland the cost is in excess of $1 billion.

The solution to the problem here was not as expensive, but just as complicated.

“It’s not an easy fix. It’s property to property, pipe by pipe.”

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